Impulse sender



J y 1949- H. J. M CREARY 2,475,553

IMPULSE ISENDER Original Filed March 10, 1945 A4a A5a A6 A7aA8 m s E: E

Al A2 E A3 INVENTOR. HAROLD J. M CREARY ATTORNEY Patented July 5, 1949*U'NliTiED TAT-ES iT i'O-FF 1 CE IMPULSE SENDER .uHarold. J 'McCreary,Lombard,.-.Ill., assignortto .AutomaticLElectric Laboratories;Inc;,'.lGhicago, "Ill.,.a corporation of Delaware :iOriginalapplication" March 10," 1945,- Serial 7N0. 5811983. .TDivided'. andthiiapplicationhpfll 26, l 1-947, Serial No. 744,176

6 Claims. 1

The present invention relates inv general to impulse. senders. and-in.particular to. improvements .in. impulse sendersainhwhichdigitvalues tobe transmitted .are charges on condensers. v

Several methods haveflbeen proposed in the registered as 1 correspondingpast. for...sequentially..charging.a series of condensers topotentialscorresponding to digit values by successive. operation of keysrepresenting digit values and thereafterutilizing the charges stored.on. the. condensersto'control. the number of impulses transmittedi in.each of a-se'ries of groups ofimpulses byaniimpulse generator. Examplesof, previously ..proposed..methods are .those disclosed in ;.Patents12,251-,666; 2,268,859; and

1.2;3232019; all issued to Hinrich Dohle. In the first twoofthe.citedpatentsthe register condensers .are connectedv to a sourceofpotential for apredetermined. interval. ofmtime inseries with avresistoi. the value of which .variesin accordance with "thedigit beingregistered. In the last one of. the

. cited. patents ..the. registercondensers are connected. for a.predetermined time interval to. a

. tap ona voltageLdivider having. a-plurality of'tapsea'ch.corresponding-to a. particular .digit value. In each. of these.casesthe register condenseris charged in series with. a. resistor and itis therefore required that .thedigit selectingkeys be held operated fora sufiicient length of .time to insure that .the register condenserreaches the desired.

final charge. I .Inthe presentinvention auxiliary normally chargedcondensers .oi different capacities are. each associated withacorresponding'one of a series of. digit selectingkeys. .When.a digitselecting key is operated theauxiliary condenser associated therewithisconnected inrmultiple with a register condenscnthereby. causing theregister condenser. .to acquire a definite. charge instantaneously. Thisapplication is adivision of copending. application? Serial 'No'.581,983, filed. March 10, 19.45 ,nowpatent N 0.1 $483,708.

The principal. object of, the: present invention is. toprovidean.impulse-sender.- employing con- Jden'sersior. registeringdigit .valuesin which a register condenser is chargedinstantaneously toa. predetermined potentialin response to the operation Qfadigitselecting. key.

..A further. object ofithe invention is-toprovide an imp'ulse senderernploying. condensers ior. reg- .;istering.i digit: values.inzwhich:ithetichargetplaced .on'a register condenser is-governedubythe capacity of. a series oft-auxiliary condensers .all of which areinitially charged to the same potential and.any:one ofswhich-may bemomentarily connected to a registercondenser.

. A; still furtherobjectoi the .invention is to pro-.vide.an..impulse..sender in-accordance with the .preceding objects thatisoperative to start the transmission of..impulses in response to theregis- 10.-

.trationofapredetermined number of digits and is thereafter.operativetotransmit subsequently I registereddigits in response to theirregistration.

..Other obj ectsof .the inventionwill appear upon -a further. perusalzof.the specification taken in ..conjunction with .lthe accompanyingdrawing Whichillustratesan; embodiment of the invention ..inlthe form ofaschematic diagram.

JBrifly'desc-ribed, theimp'ulse sender comprises a..s'et..of .tenjdigit.selecting. keys eachv of which has one. of. .ten condensers of.different. capacities associated with it. -lAll of these ten. condensersare -..norma1lycharged. A further seriesv of condensers, .all ofthesame. capac'ityare provided; there being one for. eachidigit inithenumber .to be registered.

Il'Ihe, digit selecting. keys. are each arranged to con-- nectjtheir.associatedcondenser to. af'first one of .the register.coridensersthrou'gh the wipers of a rotary switch when operated, andare.further. arranged tocauselthe rotary switch to advance to a second oneof'the register condensers when released. "Sincefthe energy stored ineach of the condensers associated with'the digit selecting keys variesin accordance withthe'digit values represented by thekeyathe registercondensers acquire charges in accordancewiththe digit values which xareto betransmitted. A. second rotary switch ..is proyidedi forsuccessively connecting. the regthe bre'al; period.oitheimpulsesand toconnect .theauxiliary. condenser .in multiple with the registercondenser.duringthemake period of theimpulses. 'L'The. auxiiiarycondenseridischargesand 'chargesinthe reversedirection during the makeperiod toiamextentidetermined by thecharge re maining on the registercondenser whereby a definite increment of charge is abstracted from theregister condenser for each impulse. The impulse generator is arrangedto concurrently transmit impulses to an output circuit to controlautomatic telephone switches or the like. When a number of impulsescorresponding to the initial charge on the register condenser have beentransmitted the remaining charge on the register condenser will havebeen reduced to a point where the gaseous discharge tube associated withthe impulse counting circuit is enabled to fire and thereby stopsfurther transmission of impulses over the control circuit for apredetermined time interval after which the second rotary switch isadvanced to the next register condenser and the second series ofimpulses is counted. Circuit arrangements are provided whereby all orthe digits to be transmitted may be registered and the transmissionstarted when desired by the operation of a start key, or whereby thetransmission may be automatically started after any desired number 01digits have been registered after which subsequently registered digitsare transmitted as they are registered. Further circuit arrangements areprovided whereby each of the digits may be transmitted in response toits registration.

The invention will now be described in detail with reference to thedrawing. The digit selecting keys Al to All and their associated digitselecting condensers Bl to B0 are shown at the upper left. Below thedigit selecting keys are two rotary switches C and D. These rotaryswitches may be of the general type disclosed in Patent No. 1,675,311,granted June 26, 1928, to Hans Sengebusch, in which the wipers advanceone step upon each de-energization of the rotary magnet. The upper setsof wiper contacts of these two switches are connected in multiple to tenregister condensers Fl to Ft). At the upper right of the drawing thereis shown an impulse generator comprising gaseous discharge tubes TI andT2 and relay G. Below the impulse generator there are shown two furthergaseous discharge tubes T3 and T4. Tube T3 controls the number ofimpulses transmitted in a series and tube T4 controls the spacinginterval between successive series of impulses. At the top center of thedrawing are shown two keys S and E n which are used to start thetransmission of impulses and to correct errors, respectively. Twolocking type keys I and 2 which are operated when the digits are to betransmitted in response to their registration or in response to theregistration of a predetermined number of digits, respectively, areshown in the lower right hand corner.

The circuit operations will first be described in detail with theassumption that keys I and 2 are normal after which the changes incircuit operations brought about by the operation of these keys will bedescribed generally. Assuming first that a ten digit number is to besent, the digit selecting keys Al to All are successively operatedmomentarily in accordance with the desired number. If the first digit isa 3, key as will be momentarily operated completing a circuit frombattery through the upper make contacts of key A3 to the stepping magnetCM of rotary switch C to ground. Condenser B3 is disconnected frombattery and. ground and connected in parallel with condenser Fl throughthe first contact of wiper Cl by the lower two sets of contacts of keyA3. The charge which was stored in condenser B3 is instantlyredistributed between condensers B3 and Fl in proportion to theircapacities. The condensers are connected so as to make the upper side ofthe register condenser Fl negative with respect to the negative batteryterminal. When key A3 is released condenser B3 is reconnected to batteryand ground causing it to be instantly recharged and the circuit tostepping magnet CM is opened causing it to restore and advance thewipers of rotary switch C one step. Subsequent operations of the keys Alto Ail causes each one of the register condensers F2 to F0 to receive acharge in accordance with the digit value represented by the particularkey A! to A0 that is operated while the wiper Cl is connected to thatone of the register condensers. The stepping magnet CM is operated andreleased once for each operation of one of the keys Al to All causingwiper Cl to advance one step each time a digit key is re stored. Afterten operations of the digit keys wiper Cl will have rotated throughone-half a revoluation and will again be resting on the first contact.When it is desired to transmit impulses corresponding to the digitvalues which have been registered as varying charges in condensers Fl toF0 start key S is momentarily operated closing a circuit to steppingmagnet DM from battery through contacts S2 and DA. Stepping magnet DMoperates. When contacts S2 are opened magnet DM restores and advancesthe wipers of rotary switch D to the second set of wiper contacts. Thecam contacts DA are operated at this time and will remain so until thewipers again reach the first set of contacts. While wiper Dl wasstanding on the first contact it connected negative battery to the gridof tube T3. The cathode and screen grid of tube T3 are connected to atap on a voltage divider connected across the battery. This tap isadjusted so that the negative bias applied to the grid of tube T3 isslightly less than that required to prevent the tube from firing. Thustube T3 is normally fired causing the relay K connected in its anodecircult to be normally operated. Relay K in turn maintains a slow torelease relay L normally operated. When magnet DM was operated it openedthe anode circuit of tube T3 at contacts DMZ causing the tube to beextinguished and relay K to be released. When the magnet DM restored itadvanced wiper DI to the second contact thus connecting registercondenser Fl to the grid of tube T3 which prevents the tube from firingagain when contact-s DMZ reclose. When wiper Di is advanced to thesecond contact it also connects condenser 3 in multiple with condenserFl. The charge stored in condenser Fl is then redistributed betweencondensers Fl and 3 in proportion to their capacities. Thisredistributed charge is always high enough to prevent the firing of tubeT3. Relay K opened the circuit to relay L which restores after a briefdelay and closes a circuit to the impuls generator at contacts Ll. Thisimpulse generator is described in detail in my copending application,Serial No. 560,076, filed October 23, 1944, now Patent No. 2,458,283. Itwill therefore be only briefly de-- scribed here. The restoration ofrelays K and L connects ground to the anodes of tubes Tl and throughcontacts DMZ, Kl, and Ll. Tube Tl fires and operates relay G. Relay Goperates and transfers negative battery from the grid of tube T2 to thegrid of tube Tl at contacts G3. After a time interval determined by thetime constant of the resistance and capacitance in the grid circuit oftube T2 the-potential on the rid of T2 falls to a point where tube T2fires. The firing of T2 extinguisher; tube Tl due to the capacitativecoupling'between the anodes of the two tubes and thus causes the releaseof relay G. Relay G restore-s and transfers negative battery back to thegrid of T2 at contacts G3. After a further time interval determined bythe time constant of the resistance and capacitance in the grid circuitof tube Tl the potential on the grid of tube TI falls to a point wheretube Tl again fires. This cycle of operations continues as lon' asground isconnected to the anodes of the tubes. The speed of operationiscontrolled by adjustment of the voltage divider having its tap connectedto the cathodes of tubes Tl and T2, and the ratio of the operated to thereleased intervals of relay G is controlled by adjustment of the slideron the-potentiometer con nected between the gridsofthe tubes.

Each time that relay 'G operates it disconnects condenser 3 fromcondenser-Fl and connects it to ground at contacts causing condenser 3to be discharged and charged in the reverse direction to thepotential-of the battery. Relay G also opens the impulsing circuit,which is connected to automatic telephone switching apparatus or thelike, at contacts Gl. Each time that relay G restores it recloses 'th'impulsing circuit at contacts Gl and reconnects condenser 3 in multiplewith condenser Fl. Condenser 3 then di charges and recharges-in thereverse direction to an extent-depending onthe remaining charge oncondenser V Fl. The values of the condensers are so chosen that whenrelay G restores for the third time the remaining charge on condenser Flis reduced to a point where tube T3 is enabled to fire and operaterelayK. Relay K operates, opens the circuit to the impulse generator atcontacts Kl to stop further transmission of impulses, closes the anodecircuit of tube T l at contacts K2, and closes the circuit to relay Land removes negative battery from the grid of tube T4 at contacts K3.Relay L operates and opens further points in the impulse generatorcircuit and the grid circuit of tube T4 at contacts Ll and L2,respectively. Before the wiper D2 left the first contact it connectednegative battery through key l to the rid of tube T l which prevented itfrom firing] When the wiper D2 was advanced to the second contactnegative battery was connected to the grid of T4 through contacts K3 andL2. When this latter source of negative battery is opened after thetransmission of the first series of impulses'the condenser connectedbetween the grid and cathode of TG discharges through the adjustableresistor connected across it. After a time interval determined by theadjustment of this'resistor the grid potential of tube T4 reachesthe'critical value where the tube fires and operates relay M. -Re'lay Moperates and closes a circuit to magnet DM at contacts Ml. Magnet DMoperates and opens the anode circuit of tubeT3 at contactsDMz. Tube T3is thus extinguished and relay released. Relay restores and openstheanode circuit of tube T4 at contacts'KZcausing tube T l to beextinguished and relay M released. Relay M restores and opens thecircuit to DM which restores and advances the wipers Dl to D3 to thethird step. When contacts DMZ reclose tube TS will be preventedfromstriking by the potenapplied to its. grid by condenser F2. Relay Ktherefore remains releasedvand when relayL subsequently restoresthe-circuit to the impulse enabled to fire.

been transmitted or generator is again closed and negative battery isreconnected to the grid of Til to charge the condenser in its gridcircuit preparatory to measuring the next spacing interval. When wiperD2 was advanced to the third step it short-circuited condenser Fl toremove any residual charge which may have been left on the condenser.Nine more series of impulses are now counted out in the same manner asthe first except that the initial charges on condensers F2 to Ftdetermine how many operations of relay 0: are required in each series toreduce the charge on the register condenser corresponding to that seriesto the point where'tube T3 is At the conclusion of. the tenth series ofimpulses the rotary switchDl Will be advanced to the twelfth stepwherecam contacts DB operate and close a self-interrupting circuit tomagnet DM from. the break contactrof 3 E3, through the make contact ofDB, and contacts DMl and J l. The stepping magnet operatesself-interrupting to advance the wipers Dl to D3 to the first step wherecam contacts DB restore to prevent further operation of DM.

Wiper Dl connects negative battery to the grid of Til causing it to fireand operate relay K. Wiper D2 connects negative battery to the grid of Tl which prevents T l from firing when relay reoperates. A11 of theapparatus has now been restored to normal, relays K and L being operatedwhich is their normal state.

In the event that an error is made in operating the digit selecting keysthe error key E is operated. This may be done before any digits haveafter transmission has started. The contacts El open the impulsingcircuit to release the equipment controlled by the impulse sender in theevent that some of the digits have been transmitted. Contacts close ahoming circuit to stepping magnet CM in series with contacts CAM and thecam contacts CA of rotary switch C causin magnet GM to operateself-interrupting to drive the wipers Cl and C2 to the first step wherethe cam contacts CA open to stop further operation of CM. A similarhoming circuit is closed to stepping magnet DM by contacts E3 throughcam contacts DB of rotary switch D, contacts DMl, and contacts J l whichcauses stepping magnet DM to operate self-interrupting to drive thewipers Dl to D3 to the twelfth step where contacts DB operate to preventfurther operation of DM. When the error key E is restored the circuit toDM reclosed through the break contact of E3 and the make contact of DBcausing magnet DM to advance wipers Di to D3 to the first step wherecontacts DB restore. Thus rotary switch D completes a half-revolutionregardless of whether it is offnormal or not at the time the error'keyis operated. If rotary switch D was off-normal, for example on step 3,the first digit would have already been sent and condenser Fl would beshort-eircuited by wiper D2. Operation of the error key causes thehalf-revolution of rotary switch D which was initiated by operation ofthe start key S to be completed causing wiper Dr to short-circuit all ofthe register condensers Fl to Fl) which it has not alreadyshort-circuited The rotary switches C and D are thus restored to normal,the register condensers Fl to Fl. are discharged, and the switchingequipment controlled by the impulse sender is released, in response tothe operation of the error key E.

.In the preceding description it was assumed that-ten digits were to betransmitted. -'In the event that it is desired to transmit a lessernumber of digits, say five for example, the digit selecting keys Al to Aare operated five times in accordance with the desired number causingcharges commensurate with the digits in the desired number to be storedin register condensers Fl to F as previously described. The start key isnow operated causing the impulse sender to start the transmission ofimpulses under the control of the register condensers and in additionclosing a homing circuit to stepping magnet CM of rotary switch C frombattery at contacts SI, through cam contacts CA and contacts CMI to CM.Magnet CM operates self-interrupting to drive wipers Cl and C2 to thefirst step where cam contacts CA open to prevent further operation ofCM. Impulses are transmitted under the control of register condensers Flto F5 exactly as previously described. At the conclusion of the fifthseries of impulses tube T3 fires, relays K and L operate, tube T l firesafter a predetermined time interval and operates relay M, relay M closesthe circuit to magnet DM which operates and opens the circuit to relay Kand the anode of T3, relay K restores and opens the circuit to relay Mand the anode of T4, relay M restores to open the circuit to Dm. Whenthe stepping magnet DM restores it advances the rotary switch wipers tothe seventh step. Wiper DI then connects condenser F6 to the grid of T3which fires immediately since there is no charge stored in condenser F5.Relay K operates and closes the anode circuit of T4 at contacts K2.During the brief interval during which relay K was restored relay Lremained operated and therefore tube T4 will fire immediately since thecondenser connected in its grid circuit will not be charged. Relay K,relay M, and magnet DM thus operate and restore in succession to advancethe rotary switch wipers to the first step where negative battery isconnected to the grid of tube Til by wiper D2 to prevent furtheroperation of relay M. During this homing operation contacts Li maintainthe impulse generator inoperative.

If it is desired that the impulse sender should transmit digits as theyare recorded, instead of waiting until all of the digits have beenrecorded and start key S operated, the key i may be operated. Theoperation of key i closes a circuit to relay J through wipers C2 and D3,and dis- I connects negative battery from the grid of T4. Relay Joperates. Tube T4 fires after a delay period and operates relay M. RelayM operates and prepares a circuit to the magnet DM at contacts Ml, whichcircuit is open at contacts J I. Now as soon rotary switch C is advancedin response to the operation of a digit selecting key the circuit torelay J will be opened at wiper C2. Relay J restores and closes thecircuit to DM which operates and opens the circuits to relay K and theanode of T3. Relay K restores and opens the circuits to relay M and theanode of T4. Relay M restores and opens the circuit to magnet 13122which restores and advances the wipers DI to D3 to the second step.Impulses corresponding to the charge in condenser Fl are now transmittedas before after which tube T3 fires and operates relay K causing thefiring of tube T4 and operation of relay M after the spacing interval.If no further digits have been stored relay J will be operated so thatoperation of magnet DM by contacts MI is prevented. If or when furtherdigits are stored relay J releases and permits magnet DM to operate andadvance rotary switch 1) until it again catches up to rotary 8 switch C.When all of the desired digits have been stored rotary switch C is homedto the first step by a momentary operation of key S in case there areless than ten digits in the number being transmitted. The remainingoperations of the impulse sender are the same as previously describedexcept that the rotary switch D is stopped on the first step through theoperation of relay J rather than through the connection of negativebattery to the grid of T4 by wiper D2.

If it is desired to have the impulse sender start automatically inresponse to the registration of a predetermined number of digits key 2is oper ated and key I is restored to normal. Key 2 closes a circuit torelay J through Wipers C2 and D3 and prepares a circuit from camcontacts CB through cam contacts DA. to magnet DM. This latter circuitis open at contacts DB. Since negative battery remains connected to thegrid of T4 when key 2 is operated tube T l will nor mally be deionizedand relay M will normally be released. Relay J will be released as soonas rotary switch C is advanced in response to the operation of a digitselecting key just as when key I was operated but in this case relay Mis restored so that magnet DM remains de-energized. Cam contacts CA maybe set so as to operate after rotary switch C has advanced any desirednumber of steps. If it is desired that transmission of impulses shouldstart after three digits have been stored, the contacts Cl"; are set soto operate when rotary switch C is resting on the third step. Whenrotary switch C advances to the third step in response to theregistration of two digits, cam contacts CB operate and. close thepreviously traced circuit to magnet DM. Magnet DM operates and opens thecircuits to relay K and the anode of T3. Relays L and K restore. Whenrotary switch C advances to the fourth step in response to theregistration of the third digit, cam contacts CB restore and open thecircuit to DM. Magnet DM restores and advances the wipers of rotaryswitch D to the second step. Subsequent operations are identical tothose described for the operation of key I eX-- cept that when rotaryswitch D again reaches the first step negative battery is connected tothe grid of tube T l by wiper D2 so as to prevent relay M from. beingoperated and thus preventing fur-- ther operation of magnet DM until camcontacts CB are again closed.

In the following table the voltages initially impressed on the registercondensers by each of the digit selecting condensers and the successivesteps in the reduction of the voltage across the register condenser byrepeated operations of relay G are shown for typical values of thecondensers that are suitable for use with a 48 volt battery and with agaseous discharge tube such as the type 2050 used for T3. In this tabledigits 1 to O are shown in column A. In column B are given suitablevalues of capacity in microfarads for digit selecting condensers (Al toA8) c0rresponding to the digits in column A. In column C are thevoltages that are impressed on a 2 mi. register condenser (F! to F8)after being connected in parallel with. a digit selecting condenser ofthe value shown in column B and which has been initially charged to 48volts. In column D the remaining voltage on the 2 mi. register condenserafter being connected in parallel with an initially discharged condenser3 of .1 mi. is shown. When read upwards, column D also shows thesuccessive steps in the reduction of the voltage across the registercondenser caused by 9 the connection of a .1 mt. condenser 3 in paralleltherewith which has been initially charged to 58 volts in the'oppositedirection. Thus nine operations of relay G cause a register condenserinitially charged to 30.3 volts to be discharged to 2.4 volts. The tenthoperation of relay G causes the register condenser to be completelydischarged.

While the invention has been described with a certain degree ofparticularity, it should be apparent that numerous modifications may beresorted to without departing from the spirit and scope of the inventionas defined in the appended claims.

What is claimed is:

1. In a register, a plurality of condensers, each condenser having adifferent capacity, the capacity of each condenser representing aparticular digit, a second plurality of condensers arranged in aparticular predetermined order, the capacity of each condenser of thesecond plurality being the same, means for charging said first pin--rality to a given potential, means for selectively connecting one ofsaid first plurality of condensers representing a digit to the firstcondenser oi said arrangement, the charge on said one condenserimmediately redistributed between said one and said first condenser inproportion to their capacities, said first condenser thereby acquiringproportional charge representative of the digit represented by said onecondenser, a third condenser, means operated to successively connecteach of said second plurality of condensers to said third condenser, thecharge on said first condenser immediately redistributed between saidnrst and third condenser when the connection is made thereto, said thirdcondenser thereby ac quiring a charge representative of the digitregistered on said one condenser.

2. In a register, a plurality of condensers, each condenser having adifierent capacity, the capacity of each condenser representing aparticular digit, a second plurality of condensers arranged in aparticular predetermined order, the capacity of each condenser of thesecond plurality being the same, means for charging said first pluralityto a given potential, means for selectively connecting one of said firstplurality of condensers representing a digit to the first condenser ofsaid arrangement, the charge on said one condenser immediatelyredistributed between said one and said first condenser in proportion totheir capacities, said first condenser thereby acquiring a proportionalcharge representative of the digit represented by said one condenser,third condenser having a smaller capacity than said capacity of each ofsaid second plurality of condensers, means operated to successivelg,connect each of said second plurality of condensers to said thirdcondenser, the charge on said first condenser immediately redistributedbetween said first and third condenser when the connection is made tosaid third condenser, and

means for intermittently charging and. discharging said third condenseruntilthecharge on the condenser of said plurality connectedto said thirdcondenser is dissipated to-a predetermined point, the numberv ofintermittent operations of said last means being indicative of the-digitrepresented by said one condensen 3. In a register, apluralityofcondensers, a plurality of switches, each having a normalv position andan operated position, eachswitch associated with one of. saidcondensers,.the charging circuit for each condenser completed when itsassociated switch is in its normal position, a second plurality ofcondensers arrangedina predetermined manner, each of said secondplurality ofucondensers having like capacities,connecting means normallyconnected to the first condenser of said second plurality, meansresponsive to operation of any one of said switches for connecting thecondenser associated with the operated switch to the first condenser ofsaid second plurality over said connecting means, the charge on saidconnected condenser immediately proportionately distributed between saidconnected condenser and said first condenser, said connecting meansthereafter operated responsive to said first operation of said. oneswitch for preparing a circuit for the second. condenser of said secondplurality, 'a second oper ation of any one of said switches connectingthe associated condenser with said second condenser of said secondplurality over said connecting means and said prepared circuit, saidsecond condenser of said second plurality receiving a chargeproportional to the capacity of the second connected condenser.

4. In a register, a plurality of condensers, each condenser having adifferent capacity, a second plurality of condensers arranged inpredetermined order, each of said second plurality having the samecapacity, means for charging said first plurality of condensers, meansfor selectively connecting one of said first plurality of condensers tothe first condenser of said second plurality to place a charge on saidfirst condenser proportional to the relative capacities of saidconnected condenser and said first condenser, a third condenser, keyingmeans, means operated responsive to operation of said keying means tosuccessively connect each of said second plurality of condensers to saidthird condenser, means operated to intermittently charge and dischargesaid third condenser until the charge in said connected condenser isdissipated to a predetermined point, means connected to said first andthird condenser initially operated responsive to operation of saidkeying means and maintained operated responsive to the proportionalcharge present on said first condenser, operation of said meansterminated when the value of the proportional charge is dissipated to apredetermined amount by said intermittent operating means, the operatingtime of said last means thereby being proportional to the originalcharge on the selected condenser of said first plurality.

5. In a system as claimed in claim t in which the means for successivelyconnecting each of said second plurality of condensers to said thirdcondenser are operated responsive to said termination of operation ofsaid last means due to the charge dissipation of the connectedcondenser.

6. In a system as claimed in claim 3 in which there is a third condenserhaving a capacity smaller than the capacity of said second plurality ofcondensers, a rotary switch operated to successively connect each of thecondensers of said 11 second plurality to said third condenser, thecharge on the connected condenser redistributed with said thirdcondenser in accord with their capacities when connected thereto, meansoperated to intermittently open the connection between the connectedcondenser and the third c0ndenser, and to connect said third condenserto a discharge circuit; and thereafter operated to reclose theconnection to again redistribute the charge between the condensers, saidrotary switch operated to connect a successive condenser only after thecharge on the condenser of the second plurality which has beenpreviously connected to said third condenser has been redistributed to apredetermined value.

HAROLD J. MCCREARY.

REFERENCES CITED The following referenlces are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,714,302 Fisher et a1 May 21,1929 2,002,219 Dimond May 21, 1935 10 2,110,015 Fitzgerald Mar. 1 1938FOREIGN PATENTS Number Country Date 519,353 Great Britain Mar. 21,1940

